Hi,
I have re-done the calibration of my TR3A fuel gauge a couple of
years ago and it worked fine. After a couple or trials a managed to
have both the offset and the gain right (I.e. it indicates empty when
it's empty BUT ALSO full when it is full, but that's not as
important).
On the back of the gauge, you have 2 small nuts that hold 2 posts
located inside the gauge. In the metallic housing of the gauge, there
are 2 slits (not holes) to let the thread of the post through.
The 2 said posts hold the coils producing the magnetic field that
drives the hand's shaft.
Proper positionning of these coils with respect to the hand's
rotating part (I don't not remember how the magnetic circuit looks
like at this point) is the key to the calibration. So, I took both
the sender and the gauge on the workbench, loosened the nuts and
iteratively searched for the 2 coil positions that would give me the
correct reading.
CAUTION: I remember almost crying in despair because each time I
would tighten the nuts, the coils would move enough the lose the
calibration (that's no more than a few 1/10th of a millimeter). I
don't remember how many trials it took to complete the job but I
think I was more desperate by the idea that I might never be able to
achieve a satisactory result than by the number of hours I spent.
Give it a trial, Good luck!
I have a PhD. in electical engineering but I don't think it is
required for that fix...
Francois Wildi
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